I mean PC Windows (XP, Vista, 7 and 8) which has (i believe, but i may be wrong) more copies installed and running than any other OS (including mobile OSes I still think there is more PCs than smart devices running, but i could be even more wrong :>). Anyway loosing ads income from one week will be a serious hit for google, and i bet they will think twice, before trying do any dirty moves against M$.